^+1 mostly
Very few drives, even SSDs can deliver more than 3gb/s (375 theoretical MB/s) either reading or writing, except for the odd burst.
A 2 disk RAID 0 can, theoretically, deliver 375 MB/s times 2 (or 6gb/s)
Therefore, until drives can saturate the new 6gb/s (or even get over the 3gb/s SataII) a properly implemented RAID 0 will win.
At present SATA III is only necessary for future expansion, and, imho, SSDs will soon be faster than the hardware they serve and the bottleneck will move elsewhere.